Children's and infant's swings have, of course, been available for many years. The usual swing includes a child-supporting seat suspended by hangers whose upper ends are pivotally mounted to a frame structure that rests on the floor. Some prior swings of this type are also motorized, being driven by a wind-up spring motor having a clock-type escapement with the suspended child-supporting seat functioning as a pendulum. It has also been proposed to drive swings of this type electrically from a rechargeable battery pack. Such attempts have usually involved periodically electrically rewinding the spring of the spring motor as is done, for example, with automobile clocks.
However, those attempts have not resulted in a highly marketable product for a variety of reasons. First and foremost, the running time of the prior battery-operated swings from a single battery charge is too short, the best being about 45 minutes. Also, some prior swings are unable to maintain the child-supporting seat in oscillation over the weight range of the children likely to use the swings, which range runs from about 10 lbs. to 25 lbs. That is, while some swings may operate properly when occupied by infants at the lower end of that range, they do not swing heavier children for any appreciable length of time. Actually, the weight range should run from 0 lbs. on up because it is highly desirable for the swing to be able to operate properly with no occupant so that the swing can be displayed dynamically on the showroom floor. Such a display is very effective from a merchandising standpoint.
Further, some prior swings tend to stop if the swing is not level or if the moment arm of the swing changes appreciable due to a child's squirming or shifting his weight in the seat.
Also, some prior electrically driven swings of this general type tend to be quite expensive because in order to operate for even a tolerable length of time, they require relatively large battery packs to drive relatively complex spring motor escapement mechanisms comprised of many parts, all of which increase the parts and assembly costs of those swings. Their complexity also makes them prone to failure so that their operating lives are not as long as they should be. All of the aforesaid problems have militated against the prior battery operated swings being widely accepted in the marketplace.